How To Read an Unlabeled Sales Chart

Re:How To Read an Unlabeled Sales Chart by bbrizzi on Tuesday February 05, 2013 @04:23AM (#5169871)

The first technique won't work if the sales are rounded off to the nearest pixel, which is pretty much almost always the case.

The second method won't work if the sales do not follow a Poisson distribution, for instance a product will have better sales at launch and during advertising campaigns. The sales figures don't always float around a constant average.

Also, I hadn't checked the math on the second method but the units don't add up.

On the LHS, you have [sales / pixel]x[pixels] = [sales]

On the RHS, you have ([sales / pixel]x[pixels])² = [sales]²

IIRC, the left hand side should be squared.

[ Parent | on HN ]

Re:How To Read an Unlabeled Sales Chart by sesqu on Tuesday February 05, 2013 @11:44AM (#5171585)

No, the left hand should not be squared. It's a special property of the Poisson process that applies to the numbers, not the units.

[ Parent | on HN ]

Re:How To Read an Unlabeled Sales Chart by jules on Tuesday February 05, 2013 @07:21AM (#5170265)

Both sides are unitless: sales is not in dollars but the number of sales.

[ Parent | on HN ]

Re:How To Read an Unlabeled Sales Chart by sesqu on Tuesday February 05, 2013 @11:48AM (#5171616)

The units are actually rates: sales per day.

[ Parent | on HN ]

Re:How To Read an Unlabeled Sales Chart by gus_massa on Tuesday February 05, 2013 @07:46AM (#5170348)

These methods also assume that the bottom level is 0. In this graph the bottom whirl is smaller, so probably it's a 0.

[ Parent | on HN ]